Study: Breastfeeding May Delay Onset of Breast Cancer

A new but small study on breastfeeding and breast cancer adds to the evidence showing its protective effects for moms, with this study suggesting that breastfeeding may delay the onset of breast cancer for nonsmoking moms who breastfeed for at least six months.

AICR’s continuous updates, which examine the global literature, found that breastfeeding directly reduces a mother’s risk of breast cancer; breastfeeding also may indirectly reduce the baby’s risk for cancer in later life, as it may play a role in being a healthy weight.

In this study, about 500 Spanish breast cancer survivors answered questions about breastfeeding, along with their family history, diet, and smoking habits. The women ranged in ages from 19 to 91; they had all been diagnosed and treated for their cancer from 2004 to 2009.

Regardless of family history, the nonsmoking women who breastfed their babies for over six months were diagnosed with breast cancer a decade later than the other women. Nonsmokers who did not breastfeed or did so for less than three months were diagnosed with breast cancer at an average age of 58; the nonsmokers who breastfed longer than six months were diagnosed at an average age of 68.

Smoking appeared to cancel the protection of breastfeeding: women who breastfed longer than six months but also smoked were diagnosed at an average age of 47.

Although the study was relatively small – only 26 of the women were nonsmokers who breastfed their child for over six months – the findings are consistent with other studies.

AICR’s continuous updates suggest several ways in which breastfeeding may offer protection. It may cause hormonal changes that reduce a woman’s lifetime exposure to estrogen, which is linked to increased breast cancer risk. Lactation also leads to shedding breast tissue, and that may help eliminate cells with potential DNA damage.